Somewhere in the Kremlin, tucked away deep in the basement labyrinth, is a department known simply as TWIN. In keeping with the implied dichotomy, and to keep an eye on each other, TWIN is run by two high ranking officers: Ilich Yevgeniy of KGB, Victor Nikolayevich of GRU. The two men, apart from the usual departmental rivalry, worked well together.

TWIN is not a Russian, or an original, idea. The Russians adapted it from the Germans, who called it Doppelganger. The Germans in turn had stolen it from the British in World War 1. The British called it Code Gemini.

J, as a young officer in World War 1, had worked in Code Gemini for a short time. J never forgot it.

The basic idea behind TWIN, laughably simple, is predicated on the old belief that every man, and woman, has a double Somewhere in the world. A ringer. The Russians have developed the idea to the Nth degree; where they could not find a double they made one.

A double for every enemy agent known to the Russians. They helped nature by plastic surgery when necessary. TWIN proteges were schooled, at times for years, in walking and talking, mannerisms, background and education, foibles and virtues. They were permitted to speak Russian only during the few days of leave granted each year. The rest of the time they lived in mockups, sets, of English villages, French towns, Brooklyn backwaters, Chicago slums, New York apartments. Hong Kong penthouses. Japanese farms. Peking pagodas.

They were surrounded by people who spoke only the particular language in which the "double" was being schooled. Educated speech, slang, idiom, localisms. They wore the right clothes, smoked the proper tobacco, followed the right sports in the right newspapers. Read the same books and magazines, listened to the same music, that their prototype, an agent employed by some power somewhere on the planet, read and listened to. When possible, scars and dental work were duplicated, as were hobbies and skills and, in some cases, even sexual perversions.

Some of the doubles were never used. They retired, with generous pensions, and were usually given a new Zil sedan. Working in TWIN was a life-time career; you aged exactly as your counterpart aged; you retired when your counterpart retired. If, for some reason, your counterpart came out of retirement, so did you. Just on the chance that you might be of some service to The Party. And make some slight return for the millions of rubles spent on you.

Because it all cost a great many billions of rubles over the years. There was grumbling and muttering among the budget men. Every year TWIN had to fight for its life, justify its existence, and every year it managed to scrape through.

J, some years before, had managed to penetrate TWIN. His man, known in the MI6A files as Monster, was an absolute duplicate of J himself. It was a delicious irony and, for one of the few times in his professional career, J found it hard to keep the secret. He was nearly tempted to go into Kensington Green some night and dig a hole and whisper into it. A thing like that should be shared. This being impossible, J contented himself with the next best thing - when he retired and wrote his book, and when the J in Moscow also retired, then he would tell the world about it.

In the meantime J, alone in his office, his stomach throbbing, stared at the bit of paper he had just taken from his IN basket.

The Russian Richard Blade had left Moscow two weeks ago.

Two weeks. J's stomach fluttered like a gaffed fish. He reached for one of the phones on his desk, telling himself not to panic. He didn't know anything yet. And yet, as he waited for the trunk call to Dorset, his skin crawled. He told himself not to be a fool. There could be a thousand reasons why the pseudo Richard Blade had left Moscow. A vacation, a love affair, a training mission of some sort. An operation in a far part of the world having nothing to do with PDX.

J drummed on the desk and opened a drawer to search for his best spare pipe. He managed a smile at himself. Hell! He had been with Blade, the real Blade, only two days before.

Sitting right in this office, talking about the upcoming trip into Dimension X.

He found the pipe and a pouch of tobacco. But had it been the real Richard Blade?

J bit hard on the pipe stem. In this jet age you could get from Moscow to London, or Dorset, in two hours. Forget two weeks!

J nodded to himself. The trouble was here. The law of averages had run out. From now on he must exercise great caution, watch every P and examine every Q, dot every I and cross every T.

Then he smiled. His stomach eased a bit. He had one sure and infallible check. Even granted that the Russians had stumbled onto PDX - he could not see how - but even if they knew about it, and were trying for a plant, they must be sure to fail. No Russian had ever been out into Dimension X. Only the real Richard Blade had done that. Only the real Richard Blade could answer questions about the dangers and the weird adventures that had befallen him after be went through the computer.

J smiled again. Then immediately frowned. What, then, were the bastards up to? It would nag him now, he would never have any peace, until he knew.

The call to Dorset went through. A girl answered. She sounded as though she had been crying.

"Hallo? Who is it?"

"Mr. Blade, please. Richard Blade. This is his cottage?"

"Yes. Yes, it is. But Richard isn't here just now, I'm afraid. He is down on the beach."

J glanced out his single window at the thickening fog competing with oncoming night,

"The beach, my dear?"

A sniff. Then a moist laugh. "Walking, you know. Not swimming or anything silly like that."

J frowned at the phone. The caution of years could not be shaken off. And yet it was probably nothing - just another quarrel with another of Blade's girls. He had had a lot of them lately. Trying to find another Zoe.

J said: "Who are you, young lady?"

"Mary. Mary Hetherton. I - I'm a friend of Richard's." Silence. Then what J could only identify as a sob.

"I really must speak with him, Miss Hetherton. I wonder if you would be so kind - ?"

"Of course. Hold on. He can't be very far."

But it was five minutes - J watched the little clock on his desk - before Blade came on the line. "Hallo?"

"Richard? This is J, dear boy. How are you?"

"I'm fine, sir." Blade sounded puzzled. "Why, sir? Shouldn't I be?"

J nodded and smiled at his end of the line. No mistaking that voice, that cheerful, well-spoken, light baritone. This was the man who had worked for him, for MI6 before it had become MI6A, ever since J had, in person, recruited him at Oxford.

Wasn't it?

"Just being conversational," J said with a laugh. "And, of course, a bit of business. A certain boffin wants to see you right away, Richard."

Unthinkable now to waste two precious days. It might already be too late. There was a tiny snapping sound. J stared down at his spare pipe, the stem broken in half in his palm. You, he told himself, had bloody well pull yourself together and bloody fast, too.

Blade said: "Lord L, eh? I didn't think it was quite ready yet, sir. Not that I mind coming up at once, but the last time I saw you I got the impression that - "

J leaped at it. "Oh, that - er, yes. When did I see you last, Richard? My memory is getting fuzzy these days."

Silence. The wire hummed in desolation. J thought he heard gulls screaming in the background. He guessed at the puzzlement on Blade's face. The lad knew there was nothing wrong with his, J's, memory.

Blade did sound puzzled. Cautious. Remote now. J smiled. Blade was a professional like himself.

"Day before yesterday, sir. In your office."

"Right," said J. "That will be all, Richard. Get up here at once, as soon as you hang up. Go to Lord L's place. You know it?"

But now Blade wasn't giving anything away. All he said was, "I know it, sir. At once. Goodbye."

"Goodbye, Richard."

J hung up and sat staring down at the broken pipe. Were his nerves really all that strung up? He tossed the bits of pipe into a wastebasket and reached for another phone. No time to waste now.

As he worked he stared occasionally out the window. Here, in the city, just off Threadneedle Street, it was quiet. Raining again, adding to the murk. There was no shimmer of neon, no street noise. The brokers and the merchants had gone for the day.

J locked his door, a thing he had not done in years. Before he went back to his desk he went again to peer out the window. Out there somewhere, perhaps not in London, or even in England, but somewhere, was another Richard Blade. A double, twin, doppelganger, call him what you would. He was there. As perfect a replica of the real Blade as years of training could make him.

J went to his files and unlocked them. He found a manila folder and scanned it rapidly. The Russian version of Blade had been in the works for some ten years. They had never used him.

Why now?

Could the Russians, impossible and incredible as it seemed, somehow have found out about PDX? Dimension X?